Inkjet printhead with self-clean ability for inkjet printing

ABSTRACT

Described is a process for producing an inkjet printhead comprising an aperture face having an oleophobic surface. The process includes forming an aperture plate by disposing a silicon layer on an aperture plate; using photolithography to create a textured pattern on an outer surface of the silicon layer; and chemically modifying the textured surface by disposing a conformal, oleophobic coating on the textured surface. The oleophobic aperture plate may be used as a front face surface for an inkjet printhead.

RELATED APPLICATIONS

Commonly assigned U.S. patent application Ser. No. 12/647,945, filedDec. 28, 2009, entitled “Superoleophobic and Superhydrophobic DevicesAnd Method For Preparing Same,” which is hereby incorporated byreference herein in its entirety, describes a process for preparing aflexible device having a textured superoleophobic surface comprisingproviding a flexible substrate; disposing a silicon layer on theflexible substrate; using photolithography to create a textured patternon the substrate wherein the textured pattern comprises an array ofpillars; and chemically modifying the textured surface by disposing aconformal oleophobic coating thereon; to provide a flexible devicehaving a superoleophobic surface and, in embodiments, to provide aflexible device having a surface that is both superoleophobic andsuperhydrophobic.

Commonly assigned U.S. patent application Ser. No. 12/648,004, filedDec. 28, 2009, entitled “A Process For Preparing An Inkjet Print HeadFront Face Having A Textured Superoleophobic Surface,” which is herebyincorporated by reference herein in its entirety, describes a processfor preparing an inkjet print head front face or nozzle plate having atextured superoleophobic surface comprising providing a siliconsubstrate; using photolithography to create a textured pattern on thesubstrate; and optionally, modifying the textured surface by disposing aconformal oleophobic coating thereon; to provide an inkjet print headfront face or nozzle plate having a textured superoleophobic surface.

Commonly assigned U.S. patent application Ser. No. 12/647,977, filedDec. 28, 2009, entitled “Superoleophobic Surfaces and Method ForPreparing Same,” which is hereby incorporated by reference herein in itsentirety, describes a process for preparing a flexible device having asuperoleophobic surface comprising providing a flexible substrate;disposing a silicon layer on the flexible substrate; usingphotolithography to create a textured pattern in the silicon layer onthe substrate wherein the textured pattern comprises a groove structure;and chemically modifying the textured surface by disposing a conformaloleophobic coating thereon; to provide a flexible device having asuperoleophobic surface.

TECHNICAL FIELD

This disclosure is directed to inkjet printheads with self-cleaningability. More particularly, described herein are inkjet printheadshaving an aperture plate coated with a superoleophobic film comprising atextured silicon layer with a conformal oleophobic coating disposed onthe textured silicon layer, and methods for preparing the same.

BACKGROUND

Fluid inkjet systems typically include one or more printheads having aplurality of inkjets from which drops of fluid are ejected towards arecording medium. The inkjets of a printhead receive ink from an inksupply chamber or manifold in the printhead which, in turn, receives inkfrom a source, such as a melted ink reservoir or an ink cartridge. Eachinkjet includes a channel having one end in fluid communication with theink supply manifold. The other end of the ink channel has an orifice ornozzle for ejecting drops of ink. The nozzles of the inkjets may beformed in an aperture or nozzle plate that has openings corresponding tothe nozzles of the inkjets.

During operation, drop ejecting signals activate actuators in theinkjets to expel drops of fluid from the inkjet nozzles onto a recordingmedium. By selectively activating the actuators of the inkjets to ejectdrops as the recording medium and/or printhead assembly are movedrelative to one another, the deposited drops can be precisely patternedto form particular text and graphic images on the recording medium. Anexample of a full width array printhead is described in U.S. PatentApplication Publication No. 2009/0046125, which is hereby incorporatedby reference herein in its entirety. An example of an ultra-violetcurable gel ink that can be jetted in such a printhead is described inU.S. Patent Application Publication No. 2007/0123606, which is herebyincorporated by reference herein in its entirety. An example of a solidink that can be jetted in such a printhead is the Xerox Color Qube™ cyansolid ink available from Xerox Corporation. U.S. Pat. No. 5,867,189,which is hereby incorporated by reference herein in its entirety,describes an inkjet print head including an ink ejecting component whichincorporates an electropolished ink-contacting or orifice surface on theoutlet side of the printhead.

One difficulty encountered with fluid inkjet systems is wetting,drooling, or flooding of inks onto the printhead front face. Thiscontamination of the printhead front face can cause or contribute toblocking of the inkjet nozzles and channels, which alone or incombination with the wetted, contaminated front face, can cause orcontribute to non-firing or missing drops, undersized or otherwisewrong-sized drops, satellites, or misdirected drops on the recordingmedium and thus result in degraded print quality. Current printheadfront face coatings are typically sputtered fluoropolymer coatings, suchas those from PTFE and PFA. When the printhead is tilted, a UV gel inkat a temperature of about 75° C. (75° C. being a typical jettingtemperature for UV gel ink) and a solid ink at a temperature of about105° C. (105° C. being a typical jetting temperature for solid ink) donot readily slide on the printhead front face surface. Rather, theseinks flow along the printhead front face and leave an ink film orresidue on the printhead that may interfere with jetting. Thus, thefront faces of UV and solid ink printheads are prone to be contaminatedby UV and solid inks. In some cases, the contaminated printhead can berefreshed or cleaned with a maintenance unit. However, this approachintroduces system complexity, hardware cost, and sometimes reliabilityissues.

There remains a need for materials and methods for preparing deviceshaving superoleophobic characteristics alone or in combination withsuperhydrophobic characteristics. Further, while currently availablecoatings for inkjet printhead front faces are suitable for theirintended purposes, a need remains for an improved printhead front facedesign that reduces or eliminates wetting, drooling, flooding, and/orcontamination of UV or solid ink over the printhead front face. Therealso remains a need for an improved printhead front face design that isink phobic, that is, oleophobic, and robust to withstand maintenanceprocedures such as wiping of the printhead front face. There furtherremains a need for an improved printhead that is easily cleaned or thatis self-cleaning, thereby eliminating hardware complexity, such as theneed for a maintenance unit, reducing run cost, and improving systemreliability.

The appropriate components and process aspects of each of the foregoingU.S. Patents and Patent Application Publications may be selected for thepresent disclosure in embodiments thereof. Further, throughout thisapplication, various publications, patents, and published patentapplications are referred to by an identifying citation. The disclosuresof the publications, patents, and published patent applicationsreferenced in this application are hereby incorporated by reference intothe present disclosure to more fully describe the state of the art towhich this invention pertains.

SUMMARY

Described is a process for producing an inkjet printhead comprising anaperture face having a highly oleophobic surface, or a superoleophobicsurface, or a surface that is both superoleophobic and superhydrophobic.The process comprises providing an aperture plate; disposing a siliconlayer on a surface of the aperture plate; using photolithography tocreate a textured pattern on an outer surface of the silicon layer, thetextured pattern comprising a groove structure or an array of pillars;and chemically modifying the textured surface by disposing a conformal,oleophobic coating on the textured surface. The superoleophobic apertureplate may be used as a front face surface for an inkjet printhead.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view of an inkjet printhead havinga layer of silicon disposed on the outer surface of the aperture plate.

FIG. 2 is a schematic top view representation of an aperture platebefore being coated with the silicon layer for an exemplary inkjetprinthead.

FIG. 3 is an illustration of a process scheme for preparing afluorinated, textured surface on an aperture plate.

FIG. 4 is an illustration of another process scheme for preparing afluorinated, textured surface on an aperture plate.

FIG. 5 is an illustration showing the states of liquid droplets ontextured surfaces.

FIG. 6 is a micrograph of a fluorosilane-coated textured surfacecomprising groove structures having textured (wavy) sidewalls.

FIG. 7 is an alternate view of the surface of FIG. 6.

FIG. 8 is a micrograph of a fluorosilane-coated textured surfacecomprising an array of pillar structures having textured (wavy)sidewalls.

FIG. 9 is an enlarged view of a portion of the surface of FIG. 8 showingdetails of the wavy sidewall pillar structure.

FIG. 10 is a micrograph of a fluorosilane-coated textured surfacecomprising an array of pillar structures having an overhang structure.

FIG. 11 is an enlarged view of a portion of the surface of FIG. 10showing details of the over-hang feature.

FIG. 12 is a micrograph of a superoleophobic textured surface comprisingan array of pillars having a 1.1 micrometer pillar height.

FIG. 13 is a micrograph of a superoleophobic textured surface comprisingan array of pillars having a 3.0 micrometer pillar height.

FIG. 14 comprises photographs showing sessile drops of water, hexadecane(HD), and solid ink on the groove structure from the parallel (leftcolumn) and perpendicular (right column) direction.

EMBODIMENTS

The word “printer” as used herein encompasses any apparatus, such as adigital copier, bookmaking machine, facsimile machine, multi-functionmachine, etc., that performs a print outputting function for anypurpose, including chemical and bioassay printed thin film devices,three-dimensional model building devices, and other applications.

Oleophobic refers to a property of a surface that is oil phobic (noaffinity) with a hydrocarbon-based liquid, such as hexadecane. Thegreater the contact angle, the greater the oleophobicity of the surface.Surfaces that exhibit a liquid hydrocarbon contact angle greater thanabout 90° may be referred to as highly oleophobic, and surfaces thatexhibit a liquid hydrocarbon contact angle greater than about 150° maybe referred to as superoleophobic. However, it is to be understood thatdifferent liquid hydrocarbons may exhibit different contact angles witha given surface and, thus, the terms oleophobic, highly oleophobic, andsuperoleophobic as used herein are used to refer to a general propertyor characterization of the surface, and is not intended to describe aspecific range of hydrocarbon contact angles.

Hydrophobic refers to a property of a surface that is phobic to water.The greater the contact angle, the greater the hydrophobicity of thesurface. Surfaces that exhibit a water contact angle greater than about120° may be referred to as highly hydrophobic, and surfaces that exhibita water contact angle greater than about 150° may be referred to assuperhydrophobic. However, it is to be understood that different liquidsmay exhibit different contact angles with a given surface and, thus, theterms hydrophobic, highly hydrophobic, and superhydrophobic as usedherein are used to refer to a general property or characterization ofthe surface, and is not intended to describe a specific range of watercontact angles.

For convenience, the embodiments disclosed herein will be described inconjunction with the manufacture of one form of an inkjet printheadshown in FIG. 1 and as described in greater detail in U.S. Pat. No.5,867,189 to Whitlow et al. It is to be understood that embodiments arenot limited to the manufacture of this particular type of inkjetprinthead. Instead, the disclosure has broad applicability to inkjetprinthead manufacture in general where it is desired to provide anaperture plate with a textured, oleophobic surface. The disclosureapplies to inkjet printheads that dispense inks that are liquid at roomtemperature as well as hot melt or phase change inks that are solid atroom temperature and are melted for ejection.

FIG. 1 illustrates an inkjet printhead 10 having a coating disposedthereon in accordance with the present disclosure. In FIG. 1, theprinthead 10 has a body 20 comprised of a plurality of laminated platesor sheets 65 fabricated, for example, from stainless steel. These sheets65 are aligned and stacked in a superposed relationship to form ajetstack 60. Jetstack sheets 65 may be etched or otherwise configured sothat the jetstack has channels, chambers, and/or passageways. Forexample, as shown in FIG. 1, printhead 10 includes one or more inkpressure chamber 30 coupled to or in fluid communication with one ormore ink source 40.

Inkjet printhead 10 also has an aperture plate 70 that is aligned andstacked in a superposed relationship with jetstack 60. Aperture plate 70has one or more opening 50, also referred to herein as an orifice,aperture, or ink ejection nozzle, that is coupled to or is in fluidcommunication with an ink pressure chamber 30 by way of an ink passageindicated by arrows 35. Ink passes through nozzle 50 during ink dropformation. Ink drops travel in a direction along path 35 from nozzle 50towards a print medium (not shown) that is spaced from nozzle 50.

A typical inkjet printhead includes a plurality of ink pressure chambers30 with each pressure chamber 30 coupled to one or more nozzle 50. Forsimplification, a single nozzle 50 is illustrated in FIG. 1. As shown inFIG. 2, the aperture plate 70 may be configured with a plurality ofnozzles 50 or an array of nozzles 50.

Aperture plate 70 defines at least a portion of an outlet side ofprinthead 10. Disposed or deposited on at least a portion of outletsurface 71 of aperture plate 70 facing the outlet side of printhead 10is a layer of silicon 72 (not shown in FIG. 2).

The aperture plate may also be referred to as an orifice plate, nozzleplate, or printhead front face plate. The aperture plate may be made ofa suitable material or composition, such as stainless steel, steel,nickel, copper, aluminum, polyimide, and silicon, and may be of anyconfiguration suitable to the device. Aperture plates of square orrectangular shapes are typically selected due to ease of manufacture.Aperture plates may be made of stainless steel selectively plated with abraze material such as gold.

The jetstack sheets or plates, and the aperture plate, may be bondedtogether by any suitable method known in the art. In some embodiments,for example, the plates are stacked together and aligned, then subjectedto a diffusion bonding process, and then subjected to a brazing process.Brazing of inkjet printhead metal plates is described in the art, suchas, for example, in U.S. Pat. No. 4,875,619, the entire disclosure ofwhich is totally incorporated herein.

To form the silicon layer, silicon, such as α-silicon, may be disposedor deposited onto a surface of the aperture plate by any suitableprocess known in the art, such as by sputtering, chemical vapordeposition, very high frequency plasma-enhanced chemical vapordeposition, microwave plasma-enhanced chemical vapor deposition,plasma-enhanced chemical vapor deposition, and use of ultrasonic nozzlesin an in-line process, among others. The silicon layer may have anysuitable thickness, such as from about 500 to about 5,000 nm, or fromabout 1,000 to about 5,000 nm, or from about 500 to about 2,500 nm, orfrom about 2,000 to about 4,000 nm, or about 3,000 nm.

The silicon layer may be formed on the aperture plate before or afterthe aperture plate is bonded with the other plates to form the jetstack.Because α-silicon has a melting point of around 1,150° C., an apertureplate having a layer of α-silicon can be subjected to bonding methodsand/or other processes that require high heat, without melting thesilicon layer. Additionally, the nozzles may be formed before or afterthe silicon layer is formed.

Textured patterns comprising a groove structure, such asmicrometer-sized grooves, or an array of pillars may be provided on thesilicon layer. The groove structure or pillar may comprise textured orwavy patterned vertical side walls and an overhang re-entrant structuredefined on the top surface of the groove structure or pillar, or acombination thereof. Textured or wavy side walls as used herein can meanroughness on the sidewall that is manifested in the submicron range. Insome embodiments, the wavy side walls have a 250 nm wavy structure witheach wave corresponding to an etching cycle as described herein below.

Referring to FIGS. 3 and 4, textured patterns 76 comprising a groovestructure or an array of pillars may be created on a silicon-coatedaperture plate using photolithography techniques. For example, thesilicon layer 72 on aperture plate 70 may be prepared and cleaned inaccordance with known photolithographic methods. A photoresist 74 canthen be applied onto the silicon layer 72, such as by spin coating orslot die coating. Any suitable photoresist can be selected, such asMega™Posit™SPR™ 700 photoresist available from Rohm and Haas.

The photoresist 74 can then be exposed and developed according tomethods as known in the art, typically by exposure to ultraviolet lightand exposure to an organic developer such as a sodium hydroxidecontaining developer or a metal-ion free developer such astetramethylammonium hydroxide.

A textured pattern 76 comprising a groove structure or an array ofpillars can be etched by any suitable method as known in the art.Generally, etching can comprise using a liquid or plasma chemical agentto remove layers of the silicon that are not protected by the mask 74.Deep reactive ion etching techniques can be employed to produce thegrooved structure with wavy sidewall.

After the etching process, the photoresist can be removed by anysuitable method. For example, the photoresist can be removed by using aliquid resist stripper or a plasma-containing oxygen. The photoresistcan be stripped using an O₂ plasma treatment such as the GaSonics Aura1000 asking system available from Surplus Process Equipment Corporation,Santa Clara, Calif. Following stripping, the substrate can be cleaned,such as with a hot piranha cleaning process.

After the surface texture is created on the silicon layer, the surfacetexture can be chemically modified. Chemically modifying the texturedsubstrate as used herein can comprise any suitable chemical treatment ofthe substrate, such as to provide or enhance the oleophobic quality ofthe textured surface. For example, the textured substrate surface may bechemically modified by disposing a self-assembled layer ofperfluorinated alkyl chains onto the textured silicon surface. A varietyof techniques, such as molecular vapor deposition, chemical vapordeposition, or solution coating may be used to deposit theself-assembled layer of perfluorinated alkyl chains onto the texturedsilicon surface. The self-assembled layer may comprise perfluorinatedalkyl chains selected fromtridecafluoro-1,1,2,2-tetrahydrooctyltrichlorosilane,tridecafluoro-1,1,2,2-tetrahydrooctyltrimethoxysilane,tridecafluoro-1,1,2,2-tetrahydrooctyltriethoxysilane,heptadecafluoro-1,1,2,2-tetrahydrooctyltrichlorosilane,heptadecafluoro-1,1,2,2-tetrahydrooctyltrimethoxysilane,heptadecafluoro-1,1,2,2-tetrahydrooctyltriethoxysilane, a combinationthereof, and the like.

In a specific embodiment, the Bosch deep reactive ion etching processcomprising pulsed or time-multiplexed etching is employed to create thetextured groove surface structure. The Bosch process can use multipleetching cycles with three separate steps within one cycle to create avertical etch: 1) deposition of a protective passivation layer, 2) Etch1, an etching cycle to remove the passivation layer where desired, and3) Etch 2, an etching cycle to etch the silicon isotropically. Each steplasts for several seconds. The passivation layer is created by C₄F₈ thatis similar to Teflon® and protects the entire substrate from furtherchemical attack and prevents further etching. However, during the Etch 1phase, the directional ions that bombard the substrate attack thepassivation layer where desired. The ions collide with the passivationlayer and sputter it off, exposing the desired area on the substrate tothe chemical etchant during Etch 2. Etch 2 serves to etch the siliconisotropically for a short time (for example, from about 5 to about 10seconds). A shorter Etch 2 step gives a smaller wave period (5 secondsleads to about 250 nanometers) and a longer Etch 2 yields longer waveperiod (10 seconds leads to about 880 nanometers). This etching cyclecan be repeated until a desired groove height or pillar height isobtained. This etching cycle can be repeated until a desirable pillarheight is obtained. In this process, pillars can be created having atextured or wavy sidewall wherein each wave corresponds to one etchingcycle.

Therefore, in some embodiments, photolithography comprises usingmultiple etching cycles to create a vertical etch wherein each of themultiple etching cycles comprises a) depositing a protective passivationlayer, b) etching to remove the passivation layer where desired, and c)etching the silicon isotropically; and d) repeating steps a) through c)until a desirable groove structure configuration is obtained. In thisprocess, a groove structure can be created having a textured or wavysidewall wherein each wave corresponds to one etching cycle. The groovestructure may include wavy sidewalls, an overhang re-entrant structure,or a combination thereof.

The periodic “wave” structure may be any suitable size. For example, thesize of each “wave” of the wavy sidewall of the groove structure may befrom about 100 nm to about 1,000 nm, such as from about 100 nm to about600 nm, or from about 400 nm to about 1,000 nm, or about 250 nm.

An embodiment of the present process comprises creating on an apertureplate a textured surface having an overhang re-entrant structure orstructures. This process comprises an analogous process using acombination of two fluorine etchings processes (CH₃F/O₂ and SF₆/O₂).Referring to FIG. 4, the process comprises providing an aperture plate200 having disposed thereon a cleaned silicon layer 201, depositing anSiO₂ thin film 202 on the cleaned silicon layer 201, such as viasputtering or plasma enhanced chemical vapor deposition, applying aphotoresist material 204 to the silicon oxide 202 coated silicon layer201 on aperture plate 200, exposing and developing the photoresistmaterial 204, such as with 5:1 photolithography using SPR™ 700-1.2photoresist, using fluorine-based reactive ion etching (CH₃F/O₂) todefine a textured pattern 206 in the SiO₂ layer comprising a groovepattern or an array of pillars in the SiO₂ layer, using a secondfluorine-based (SF₆/O₂) reactive ion etching process, followed by hotstripping, and piranha cleaning to create the textured pattern 208having overhang re-entrant structures 210 on the topmost layer. Thetextured pattern 206 can then be coated with a conformal oleophobiccoating 212 to provide a superoleophobic aperture plate comprising atextured grooved pattern having an overhang re-entrant structure on thetop surface thereof or comprising a textured pattern of pillars havingstraight side walls and overhang re-entrant structures.

The aperture plate having an oleophobic surface may be prepared usingroll-to-roll web fabrication technology. For example, a roll comprisinga substrate passes through a first station where a layer of amorphoussilicon is deposited on the substrate, such as by chemical vapordeposition or sputtering, followed by slot die coating with photoresist,followed by a second station comprising a masking andexposing/developing station, followed by an etching station, followed bya cleaning station. The textured substrate can then pass through acoating station where the textured substrate can be modified with aconformal oleophobic coating.

FIG. 5 depicts the two states commonly used to describe the compositeliquid-solid interface between liquid droplets on rough surfaces. InFIG. 5, a surface modified with a textured pattern 300 is shown where aliquid droplet 302 is shown in the Cassie-Baxter state and the Wenzelstate. The static contact angles for the droplet 302 at theCassie-Baxter state (θ_(CB)) and the Wenzel state (θ_(W)) are given byequations (1) and (2), respectively:

cos θ_(CB) =R _(f) f cos θ_(y) +f−1  (1)

cos θ_(W) =r cos θ_(y)  (2)

where f is the area fraction of projected wet area, R_(f) is theroughness ratio on the wet area and R_(f) f is solid area fraction, r isthe roughness ratio, and θ_(y) is the contact angle of the liquiddroplet with a flat surface.

In the Cassie-Baxter state, the liquid droplet “sits” primarily on airwith a very large contact angle (θ_(CB)). According to the equation,liquid droplets will be in the Cassie-Baxter state if the liquid and thesurface have a high degree of phobicity, for example, when θ_(y)≧90°.

With respect to hydrocarbon-based liquid, for example, ink, asexemplified by hexadecane, the textured surfaces comprising a groovestructure having overhang re-entrant structures formed on the topsurface of the groove structure renders the surface “phobic” enough(that is, θ_(y)=73°) to result in the hexadecane droplet forming theCassie-Baxter state at the liquid-solid interface of the textured,oleophobic surface.

FIG. 6 is a micrograph of a structure comprising fluorosilane-coatedgrooves 3 micrometers in width and 6 micrometers in pitch. FIG. 7provides an alternate view of the structure of FIG. 6, showing the wavyside wall structure with the top surface forming an overhang re-entrantstructure.

FIG. 8 is a micrograph of a fluorosilane-coated textured surfacecomprising an array of pillar structures having textured (wavy)sidewalls. FIG. 9 provides an enlarged view of a portion of the surfaceof FIG. 8, showing details of the wavy side wall pillar structure. FIG.10 provides a micrograph of a fluorosilane-coated textured surfacecomprising an array of pillars having overhang re-entrant structuresdefined on the top of the pillars. FIG. 11 provides an enlarged view ofa portion of the surface of FIG. 10 showing details of the overhangre-entrant feature.

The groove structure can have any suitable spacing or density or solidarea coverage. For example, the groove structure may have a solid areacoverage of from about 0.5% to about 40%, or from about 1% to about 20%.

The groove structure can have any suitable width and pitch. For example,the grove structure may have a width of from about 0.5 to about 10micrometers, or from about 1 to about 5 micrometers, or about 3micrometers. Further, the groove structure may have a groove pitch offrom about 2 to about 15 micrometers, or from about 3 to about 12micrometers, or about 6 micrometers.

The groove structure can have any suitable shape. The overall groovestructure can have a configuration designed to form a specific pattern.For example, the groove structure can have a configuration selected todirect a flow of liquid in a selected flow pattern.

The groove structure can be defined at any suitable or desired totalheight. The textured surface may comprise groove pattern having a totalheight of from about 0.3 to about 5 micrometers, or from about 0.3 toabout 4 micrometers, or from about 0.5 to about 4 micrometers.

The pillar array can have any suitable spacing or pillar density orsolid area coverage. The array of pillars may have a solid area coverageof from about 0.5% to about 40%, or from about 1% to about 20%. Thepillar array can have any suitable spacing or pillar density. Forexample, the array of pillars may have a pillar center-to-pillar centerspacing of about 6 micrometers.

The pillar array can have any suitable shape, such as round, elliptical,square, rectangular, triangle, star-shaped, or the like.

The pillar array can have any suitable diameter or equivalent diameter.For example, the array of pillars can have diameter of from about 0.1 toabout 10 micrometers, or from about 1 to about 5 micrometers.

The pillars can be defined at any suitable or desired height. Forexample, the textured surface can comprise an array of pillars having apillar height of from about 0.3 to about 10 micrometers, or from about0.3 to about 4 micrometers, or from about 0.5 to about 3 micrometers.

In FIG. 12, a micrograph shows a superoleophobic textured surfacecomprising an array of pillars having a 1.1 micrometer pillar height. InFIG. 13, a micrograph shows a superoleophobic textured surfacecomprising an array of pillars having a 3.0 micrometer pillar height.

The surface properties of the fluorinated textured surfaces were studiedby determining both static and dynamic contact angle measurements. FIG.14 is a set of photographs showing sessile drops of water, hexadecane(HD), and solid ink from the parallel direction and the perpendiculardirection on fluorosilane-coated textured surfaces prepared on a siliconwafer comprising groove structures.

While not wishing to be bound by theory, the inventors believe that thehigh contact angles observed for the FOTS textured surface with waterand hexadecane is the result of the combination of surface texturing andfluorination. In specific embodiments, the textured devices comprise atleast one of a wavy side wall feature or an overhang re-entrantstructure at the top surface textured structure to provide flexiblesuperoleophobic devices. The inventors believe that the re-entrantstructure on the top surface of the groove structure and pillarstructure is a significant driver for superoleophobicity.

Superoleophobic films prepared using photolithography via theroll-to-roll web manufacturing process and comprising textured groovepatterns or textured patterns of pillars on the flexible silicon film asdescribed herein can be processed for use as inkjet printhead parts.Nozzles may then be created on the film, for example using laserablation techniques or mechanical means (such as hole punching).Printhead size film can be cut, aligned and attached, such as glued,onto the nozzle front face plate for inkjet printhead applications. Thistextured nozzle front face will be superoleophobic and will overcome thewetting and drooling problems that is problematic in certain currentprintheads. If desired, the textured patterns may have a height of 3micrometers. Further, superoleophobicity can be maintained with patternheight as low as 1 micron. With reduced pattern height, the mechanicalrobustness of the shallow textured patterns increases. Very little to nosurface damage is observed when manually rubbing these superoleophobicpatterns.

In further embodiments, the groove structure provides improvedmechanical robustness in combination with extremely low sliding anglesin the parallel direction for an advantageous directional self-cleaningproperty, rendering its use as a self-cleaning, no-maintenance frontface for solid ink and UV ink printheads. This anisotropic wetting anddirectional cleaning can be a great advantage for areas adjacent to theedges of the nozzle as well as areas far away from the nozzle. Highcontact angle in the orthogonal direction assists with any residual inkpinning and directional self cleaning in the parallel direction helps tore-direct the ink away from the nozzle and eventually remove the inkfrom the front face. Accordingly, residual ink will not puddle in thevicinity of the nozzle nor accumulate on the front plate causingproblems such as ink wetting/drooling/flooding on the printhead frontface.

The present inventors have demonstrated that superoleophobic surfaces(for example, wherein hexadecane droplets faint a contact angle ofgreater than about 150° and a sliding angle of less than about 10° withthe surface) can be fabricated by simple photolithography and surfacemodification techniques on a silicon wafer. The prepared superoleophobicsurface is very “ink phobic” and has the surface properties verydesirable for the front face of inkjet printheads, for example, highcontact angle with ink for super de-wetting and high holding pressureand low sliding angle for self clean and easy clean. Generally, thegreater the ink contact angle the better (higher) the holding pressure.Holding pressure measures the ability of the aperture plate to avoid inkweeping out of the nozzle opening when the pressure of the ink tank(reservoir) increases.

Inkjet printheads in accordance with this disclosure comprise anaperture plate having an oleophobic surface. The oleophobic surface mayexhibit a hexadecane contact angle of from about 90° to about 175°, orfrom about 120° to about 170°, or from about 150° to about 175°, or fromabout 150° to about 160°. The oleophobic surface may also exhibit ahexadecane sliding angle of from about 1° to about 30°, or from about 1°to about 25°, or from about 1° to about 15°, or from about 1° to about10°.

The oleophobic surface may also be hydrophobic and exhibit a watercontact angle of from about 120° to about 180°, such as for example, awater contact angle of from about 130° to about 180°, or from about 150°to about 180°. The oleophobic surface may also exhibit a water slidingangle of from about 1° to about 30°, or from about 1° to about 25°, orfrom about 1° to about 15°, or from about 1° to about 10°.

Because contact angles and sliding angles vary with the size of the dropbeing tested, the contact angles and sliding angles discussed herein aremade in reference to a drop of a test substance having a volume of fromabout 5 to about 10 μL.

In some embodiments, the aperture plate comprises a superoleophobicsurface where hexadecane has a contact angle with the surface of fromgreater than about 90° to about 175° in a direction that is eitherparallel to the groove direction or perpendicular to the groovedirection. In further embodiments, the aperture plate comprises asuperoleophobic surface where hexadecane has a sliding angle with thesurface of less than about 30° in parallel to a groove direction.

Examples

The following Examples are being submitted to further define variousspecies of the present disclosure. These Examples are intended to beillustrative only and are not intended to limit the scope of the presentdisclosure. Also, parts and percentages are by weight unless otherwiseindicated.

Table 1 summarizes contact angle data and sliding angle data for anumber of relevant surfaces with water, hexadecane, solid ink, andultraviolet curable gel ink. Contact angle and sliding anglemeasurements were conducted on an OCA20 goniometer from Dataphysics(Germany), which includes a computer-controlled automatic liquiddispensing system, computer controlled tilting stage, and acomputer-based image processing system. In typical static contact angleand sliding angle measurements, test liquid droplets include about 5 to10 μL of a test substance selected from water, hexadecane, solid ink,and UV ink gently deposited on the testing surface. The static angle wasdetermined by the computer software (SCA20) and each reported data is anaverage of more than 5 independent measurements. Sliding anglemeasurements were performed by tilting the base unit at a rate of about1°/sec using titling base unit TBU90E. The sliding angle was defined andmeasured as the angle where the test liquid droplet starts to move.

Example 1 is a new stainless steel printhead (with PFA coating) frommanufacturing.

Example 2 is a used stainless printhead (with PFA coating) frommanufacturing

Example 3 is a commercial PTFE film.

Example 4 is a superoleophobic surface comprising pillar structures with3 μm dia./6 μm pitch.

Example 5 is a superoleophobic surface comprising groove structures with3 μm width/6 μm pitch, in the parallel direction.

TABLE 1 Solid ink UV ink Water Hexadecane (~105° C.) (~75° C.) ContactSliding Contact Sliding Contact Sliding Contact Sliding Example angleangle angle angle angle angle angle angle 1 ~130°  >90° ~71° ~64°  ~85~40-70 ~63 Flowing leaving thin ink film 2  ~85°  >90° ~30° Flowing N.A.N.A. N.A. N.A. leaving thin film 3 ~118° ~64° ~48° ~31°  ~63°  >90°~58° >90° 4 ~156° ~10° ~158°  ~10° ~155° ~33°-58° N.A. N.A. 5 ~131°  ~8°~113°   ~4° ~120° ~25° N.A. N.A. N.A. = not available

It will be appreciated that various of the above-disclosed and otherfeatures and functions, or alternatives thereof, may be desirablycombined into many other different systems or applications. Also,various presently unforeseen or unanticipated alternatives,modifications, variations or improvements therein may be subsequentlymade by those skilled in the art, and are also intended to beencompassed by the following claims.

1. A method for producing an inkjet printhead comprising an apertureplate having an oleophobic surface, the method comprising: disposing asilicon layer on an aperture plate; using photolithography to create atextured pattern in the silicon layer on the aperture plate to form atextured silicon surface; and chemically modifying the textured siliconsurface by depositing a conformal oleophobic coating material on thetextured surface.
 2. The method of claim 1, wherein the conformaloleophobic coating material is deposited on the textured silicon surfaceby a molecular vapor deposition technique, a chemical vapor depositiontechnique, or a solution self assembly technique.
 3. The method of claim2, wherein the conformal oleophobic coating material comprises aself-assembling fluorosilane compound.
 4. The method of claim 1, whereinthe textured pattern comprises an array of pillars, an array of pillarshaving an overhang re-entrant structure disposed on said pillars, anarray of pillars having textured, wavy sidewalls, or a combinationthereof.
 5. The method of claim 1, wherein the textured patterncomprises a groove pattern, a groove pattern including an overhangre-entrant structure, a groove pattern including textured, wavysidewalls, or a combination thereof.
 6. The method of claim 1, whereinthe textured pattern has a configuration that directs a flow of liquidin a desired flow pattern.
 7. The method of claim 1, wherein thetextured pattern comprises an array of pillars having a pillar height ofabout 0.5 to about 5 micrometers.
 8. The method of claim 4, wherein thepillars are round, elliptical, square, rectangular, triangle, orstar-shaped.
 9. The method of claim 5, wherein a height of the groovepattern is about 0.5 to about 5 micrometers.
 10. The method of claim 4,wherein the array of pillars has a solid area coverage of from about0.5% to about 40%.
 11. The method of claim 1, wherein the texturedpattern comprises pillars or groove structures having a texturedsidewall comprises a plurality of waves, each wave having an amplitudeof from about 100 nanometers to about 1,000 nanometers.
 12. The methodof claim 1, wherein the oleophobic conformal coating is formed from aprecursor comprisingtridecafluoro-1,1,2,2-tetrahydrooctyltrichlorosilane,tridecafluoro-1,1,2,2-tetrahydrooctyltrimethoxysilane,tridecafluoro-1,1,2,2-tetrahydrooctyltriethoxysilane,heptadecafluoro-1,1,2,2-tetrahydrooctyltrichlorosilane,heptadecafluoro-1,1,2,2-tetrahydrooctyltrimethoxysilane,heptadecafluoro-1,1,2,2-tetrahydrooctyltriethoxysilane, or a combinationthereof.
 13. The method of claim 1, wherein the silicon layer comprisesα-silicon.
 14. The method of claim 1, wherein the aperture platecomprises stainless steel.
 15. The method of claim 1, furthercomprising: bonding the aperture plate to a stack of one or morejetstack plates.
 16. The method of claim 15, wherein the silicon layeris disposed on the aperture plate before the aperture plate is bonded tothe stack of one or more jetstack plates.
 17. The method of claim 16,wherein the textured pattern is formed after the aperture plate isbonded to the stack of one or more jetstack plates.
 18. The method ofclaim 1, wherein the oleophobic surface exhibits a hexadecane contactangle of from about 90° to about 175°.
 19. The method of claim 18,wherein the oleophobic surface further exhibits a hexadecane slidingangle of from about 1° to about 30°.
 20. The method of claim 19, whereinthe oleophobic surface further exhibits a water contact angle of fromabout 120° to about 180°.
 21. The method of claim 18, wherein theoleophobic surface further exhibits a water sliding angle of from about1° to about 30°.
 22. An inkjet printhead comprising: an aperture plate;a silicon layer disposed on the aperture plate, an outer surface of thesilicon layer comprising a textured pattern; and a conformal oleophobiccoating disposed on the textured silicon surface.
 23. The printhead ofclaim 22, wherein the textured pattern comprises an array of pillars, anarray of pillars having an overhang re-entrant structure disposed onsaid pillars, an array of pillars having textured, wavy sidewalls, or acombination thereof.
 24. The printhead of claim 22, wherein the texturedpattern comprises groove pattern, a groove pattern including an overhangre-entrant structure, a groove pattern including textured, wavysidewalls, or a combination thereof.
 25. The printhead of claim 22,wherein the groove pattern comprises a total height of about 0.5 toabout 5 micrometers.
 26. The printhead of claim 22, wherein the texturedpattern comprises an array of pillars having a pillar height of about0.5 to about 5 micrometers.